Interpretive Summary: Melon is an economically important crop species in the U.S. and worldwide. The genetics of melon for yield and quality improvement has been systematically studied for approximately 70 years. Based in these studies the yield and quality of modern melon has improved several fold when compared to its heirloom progenitors. There is a need for a more precise scientific understanding of yield in melon in order to provide for yield improvements in the future. Biotechnology (tools that allow for the dissection of genetic attributes) has been developed in other species that can be applied to melon. Early studies using such tools has led to an improved understanding of the genes (hereditary units found in the cell that control the expression of traits) that control horticulturally important traits such as virus resistance. Genes that control yield in melon have not been investigated using these new technologies, and thus experiments were conducted that allowed for the identification of genes associated with yield (fruit number and weight, branching, flowering, etc.). Data from these experiments were used to characterize the genetic control of these traits and determine the location on chromosomes (genes arranged in a linear array) such that plant breeders and plant geneticists can now better understand and manipulate genes for yield. Results will allow for plant breeders to be more efficient in their development of new cultivars and thus allow for more rapid release of improved varies with improved yield. This will provide a competitive advantage to the U.S. grower to allow for improved sustainability in a global market.

Technical Abstract:
The inheritance of plant architecture and fruit yield in melon (Cucumis melo L.; 2n = 2x = 24) is poorly understood, and the mapping of quantitative trait loci (QTL) for yield-related traits has not been reported. Therefore, a set of 81 recombinant inbred lines (RIL) was developed from a cross between a monoecious, highly branched, line USDA 846-1 (P1) and a standard vining, andromonoecious cultivar, ‘Top Mark’ (P2). The RIL, parental lines, and three control cultivars (‘Esteem’, ‘Sol Dorado’, and ‘Hales Best Jumbo’) were grown at Hancock, Wisc. and El Centro, Calif. in 2002, and evaluated for primary branch number (PB), fruit number per plant (FN), fruit weight per plant (FW), average weight per fruit (AWF), and percentage of mature fruit per plot (PMF). A 181-point genetic map was constructed using 114 RAPD, 35 SSR, and 32 AFLP markers. Fifteen linkage groups spanned 1,032 cM with a mean marker interval of 5.7 cM. A total of 34 QTL were detected in both locations (PB = 7, FN = 10, FW = 9, AWF = 5, and PMF = 3). QTL analyses revealed four location-independent factors for PB (pb1.1, pb1.2, pb2.3, and pb10.5), three for FN (fn1.1, fn1.3, and fn5.6), four for FW (fw1.1, fw5.6, fw6.7, and fw8.8), and two for AWF (awf1.2 and awf4.3). Efficient conventional phenotypic selection coupled with marker-assisted selection could have utility for development of monoecious, highly branched germplasm with concentrated fruit set.